3.1.1 Exchange Surfaces Flashcards
what do living organisms need to keep them alive
oxygen, water, glucose, amino acids, minerals
what do living organisms need to get rid of
carbon dioxide, urea, creatinine
factors that affect the need for an exchange system
size, SA:volume, diffusion distance
metabolic rate
endotherm/ectotherm
features of an efficient exchange surface
high surface area - max. molecules can diffuse per unit time
thin cell walls - short diffusion distance, faster rate
good blood supply/ ventilation - maintains steep conc. gradient
moist - enables gases to dissolve + cells protected from drying out
permeable - gases can diffuse through cell membrane
why do smaller organisms have a lower oxygen demand
smaller organisms = lower metabolic activity, low demand for oxygen
the main function of surfactant
lowers surface tension at the air/liquid interface within the alveoli to stop the walls from sticking together and collapsing during inhalation
mechanism of breathing: ventilating the lungs - inspiration
ACTIVE
external intercostals: contract
ribs move: up and out
diaphragm: contracts
diaphragm moves: down
diaphragm shape: flattens
thorax volume: increases
thorax pressure: decreases
air: drawn in, enters
internal intercostals: relax
elastic fibres: stretch
mechanism of breathing: ventilating the lungs - expiration
PASSIVE
external intercostals: relax
ribs move: down and in
diaphragm: relax
diaphragm moves: up
diaphragm shape: domed
thorax volume: decreases
thorax pressure: increases
air: expelled, leaves
internal intercostals: relax
elastic fibres: recoil to expel air
cartilage is found in
trachea - c-shaped rings
bronchus - plates
goblet cells are found in
trachea
bronchus
ciliated cells are found in
trachea
bronchus
bronchioles
smooth muscle is found in
trachea
bronchus
bronchioles
elastic fibres are found in
trachea
bronchus
bronchioles
alveolus
squamous epithelium is found in
alveolus
function of cartilage
strong - prevents collapse of trachea and bronchus
flexible- trachea and bronchi bend/extend
c-shaped rings - oesphagus can expand behind
function of goblet cells
secrete mucus- contains glycoproteins, traps pathogens
function of ciliated cells
hair like projections beat to waft mucus up the airway
function of smooth muscle
contracts - constricts/ narrows airway e.g. if there is a harmful substance in the air
relaxes - dilate airway to increase air flow to alveoli
function of elastic fibers
bronchioles- when smooth muscle contracts, elastic fibers stretch. when smooth muscle relaxes, elastic fibers recoil
alveoli- stretch to allow alveoli to expand. recoil to expel air. prevents bursting during inhalation
function of squamous epithelium
thin, flattened cells - short diffusion distance = increased rate of gaseous exchange
why is a nose clip worn when using a spirometer
to prevent the subject from breathing via the nose
how does a spirometer work
breathe out into tank - upper half rises
breathe in from tank - upper half falls
a tracemarker is attached to mobile upper half connected to kymograph which records changes in oxygen
why does total volume in tank slowly decline
the subject uses up oxygen from tank due to gas exchange in alveolus - left in dead space
why is soda lime used in spirometer
soda lime absorbs carbon dioxide that is exhaled
why does exhaled air contain oxygen
some inhaled air does not reach the alveolus for gas exchange to occur
tidal volume
volume of air that flows in and out of the lungs with each breath during quiet breathing - usually measured at rest
vital capacity
maximum volume of air that can be moved by the lungs in one breathe
strongest possible exhalation followed by strongest possible inhalation
inspiratory reserve volume
maximum amount of air inspired in excess of the tidal volume - a normal inhalation
expiratory reserve volume
maximum amount of air expired in excess of the tidal volume
residual volume
volume left in lungs after maximum forced expiration
total lung capacity
total air in lungs after maximum inhalation
total volume lungs can hold
total air breathed per minute
tidal volume x breathing rate
how might athletic training affect the condition of the lungs
more efficient lungs - improved network of pulmonary capillaries so more oxygen is taken up
slightly increases lung volume
increase in alveoli size
increased strength in muscles - can breathe in more air for longer periods of time
faster breathing rate - more oxygen produced
higher tidal volume
why do fish have an exchange system
multicellular, move around: fairly high metabolic rate
ectotherms: cannot increase metabolic rate to maintain temperature, lower oxygen demand
fairly large - small SA:V ratio: large diffusion distance so cannot rely on simple diffusion alone
**water is thicker + denser than air: **more energy req. to cross gas exchange surfaces
structure of fish gills in bony fish
series of gills on each side of the head
each gill arch attaches to 2 rows of filaments, 1 row of gill rakers
rows of lamellae in filaments
lamellae surface consists of a single layer of flattened cells that cover a vast network of capillaries
gill rakers
made of bone or cartilage
prevents food particles reaching filaments
prevents obstruction of gas exchange
how does the structure of the gills relate to their function
lots of filaments/lamellae: provide large SA
filaments + lamellae have thin walls: short diffusion distance
filaments + lamellae increase rate of diffusion of oxygen and carbon dioxide
filament tips overlap: increases resistance to flow of water = gives time for diffusion of gases
good blood supply via capillary network in capillaries in lamellae: maintains steep concentration gradient
counter current flow of blood and water: maintains concentration gradient across full length of gill
counter current system of blood and water flow
blood and water flow in opposite directions
ensures concentration of oxygen in water is always higher than concentration of oxygen in the blood
concentration gradient can be maintained
more oxygen will diffuse into the blood
ventilation in a bony fish: inspiration
mouth opens, operculum closed
buccal cavity floor lowers (muscles req. - ATP)
buccal cavity: pressure decreases, volume increases
water flows in via mouth down a pressure gradient
sides of opercular cavity bulge outwards (muscles req. - ATP)
opercular cavity: pressure decreases, volume increases
mouth closes, buccal cavity floor rises
buccal cavity: volume decreases, pressure increases
pressure in buccal cavity > pressure in opercular cavity
water forced to flow over gills, down pressure gradient
ventilation in a bony fish: expiration
sides of opercular cavity move inwards
operculum opens
water flows in one direction over gills and is expelled
why do insects have an exchange system
fairly active + multicellular: certain oxygen demands
tough exoskeleton: impermeable to gases no exchange via skin
**small - large SA:V ratio: ** short diffusion distance, can rely on simple diffusion
tracheal system of an insect
spiracle: allows air to enter the insect
tracheae: have rigid rings of cartilage to keep it open
muscle fibres: the site of gas exchange
function of tracheae
held open byb citin
enables carbon dioxide and oxygen to diffuse down
function of trachioles
lots of trachioles increases SA
moist lining for gases to dissolve
lots of tracheal fluid at the end of trachiole which oxygen diffuses through
when insects are active
muscles anaerobically respire to produce lactic acid
decreases water potential - drawing tracheal fluid into muscles by osmosis
more air is drawn in
higher surface area of the walls exposed for diffusion
rate of diffusion increases
